There are conventional designs that use an optical device to concentrate electromagnetic radiation onto an electromagnetic radiation energy conversion device. However, these devices are limited from widespread use by their conversion efficiency and cost.
Some conventional designs concentrate electromagnetic radiation onto a single electromagnetic radiation energy conversion device, such as a solar cell. Such designs are limited by the conversion efficiency of the electromagnetic radiation energy conversion device. The electromagnetic radiation energy conversion device may be efficient in converting electromagnetic radiation to energy of another form over some portion of the electromagnetic spectrum. However, the overall efficiency of the system may be limited by the fact that a single electromagnetic radiation energy conversion device may be unable to achieve a high conversion efficiency from electromagnetic radiation to another form of energy over the entire electromagnetic spectrum or large portions of the electromagnetic spectrum.
Other conventional designs use multiple electromagnetic energy conversion devices in tandem or in layers, such as multi junction cells. Such designs improve the overall conversion efficiency of the system by using multiple electromagnetic energy conversion devices to efficiently convert multiple portions of the electromagnetic radiation spectrum into other forms of energy. However, the efficiency of such systems may be limited by the fact that there are reflective losses introduced by each electromagnetic radiation device, interface, or layer that is added. These reflective losses reduce the amount of electromagnetic radiation reaching some of the electromagnetic radiation energy conversion devices or layers. These reflective losses also reduce the overall conversion efficiency from electromagnetic radiation to another form of energy.
Some conventional designs use an optical device or optical devices to concentrate and disperse electromagnetic radiation onto multiple electromagnetic radiation energy conversion devices that are not in tandem or layers, but are placed next to one another in order to improve efficiency. Such designs use multiple electromagnetic radiation energy conversion devices to convert multiple portions of the electromagnetic radiation spectrum into other forms of energy. Such designs also reduce some of the reflective losses that plague designs, which use multiple electromagnetic radiation energy conversion devices in tandem or in layers, since the electromagnetic radiation, after concentration and dispersion, reaches each electromagnetic radiation energy conversion device without passing through other devices, layers, or interfaces. However, these designs may be limited by the design of the concentrating and dispersing optical device or devices. The design of the optical device or devices in the conventional systems may use multiple optical devices to disperse and concentrate electromagnetic radiation onto electromagnetic radiation energy conversion devices. Reflection and absorption losses may be increased by using multiple optical devices, reducing the overall efficiency of the system, for such designs.
The design of the optics according to some conventional designs may use a single optical device to concentrate and disperse electromagnetic radiation onto electromagnetic radiation energy conversion devices. Such conventional optical device designs, such as Fresnel lenses, focus each wavelength of electromagnetic radiation onto the optical axis of the optical device, as shown in FIG. 1A. In such conventional optical device designs the optical axis of the optical device is parallel to the electromagnetic radiation that is incident upon the optical device. FIG. 1A illustrates ray tracing of a conventional system, including the focal points 122, 124, and 126 of three wavelengths of electromagnetic radiation 116, 118, and 120 that are dispersed and concentrated. The optical axis of a conventional optical device is represented by a vertical line 140 in FIG. 1A. The ray trace of the three wavelengths 116, 118, and 120 of electromagnetic radiation shown in FIG. 1A shows that the focal points 122, 124, and 126 for the three wavelengths 116, 118, and 120 of electromagnetic radiation fall along the optical axis 140 of the optical device, which is parallel to the electromagnetic radiation that is incident upon the conventional optical device. The focal points 122, 124, and 126 of three different wavelengths, 116, 118, and 120 of electromagnetic radiation, relative to one another, are parallel to the electromagnetic radiation that is incident upon the conventional optical device. The positioning of the focal points 122, 124, and 126 for the three wavelengths 116, 118, and 120 along the optical axis 140 of the optical device may limit the conversion efficiency of the system. If electromagnetic radiation energy conversion devices are positioned at or near the focal points 122, 124, and 126 of the three wavelengths 116, 118, and 120 along the optical axis 140, the off-normal incident angle of the electromagnetic radiation on the electromagnetic radiation energy conversion devices may be large. A large off-normal incident angle of electromagnetic radiation on the electromagnetic radiation energy conversion devices may result in large reflection losses at the surface of the electromagnetic radiation energy conversion devices. If the electromagnetic radiation energy conversion devices are angled away from the optical axis to reduce the reflection losses caused by the large off-normal incident angle of the electromagnetic radiation on the electromagnetic radiation energy conversion devices, the electromagnetic radiation energy conversion devices are no longer positioned at or near the focal point for each wavelength of electromagnetic radiation. If the electromagnetic radiation energy conversion devices are not at or near the focal point of each wavelength of electromagnetic radiation, a blurring effect of the dispersed wavelengths will occur. If the dispersed wavelengths suffer from a blurring effect or decreased spectral separation, the overall efficiency of the system may decrease because all of the electromagnetic radiation of a given wavelength will not reach the electromagnetic radiation energy conversion device that is most efficient in converting that wavelength of electromagnetic radiation to another form of energy.
Conventional designs that use an optical device to concentrate electromagnetic radiation onto electromagnetic radiation energy conversion devices may suffer from limited efficiency due to the use of a single electromagnetic radiation energy conversion device, multiple electromagnetic radiation energy conversion devices positioned in tandem, multiple optical devices, or an optical device, which concentrates and disperses electromagnetic radiation such that the focal point for each wavelength of electromagnetic radiation is positioned along the optical axis of the optical device.
Conventional designs that use multiple discontinuous surfaces to reduce the thickness and the amount of material needed to produce an optical device may experience shading losses due to electromagnetic radiation being reflected and absorbed by draft surfaces, which connect the multiple discontinuous surfaces, and the corner sections where the draft surfaces meet the discontinuous surfaces. These losses may reduce the performance of the optical device and are especially significant for conventional designs that concentrate electromagnetic radiation in two axes.
Conventional designs that use a negative draft angle to reduce the absorption and reflection of electromagnetic radiation at the draft surfaces of an optical device with multiple discontinuous surfaces may face financial and design limitations. Producing negative draft angles for the draft surfaces of an optical device with multiple discontinuous surfaces may require the use of multiple mold pieces, which may add to the cost of the optical device. Conventional designs may have negative draft angles for the draft surfaces of an optical device with multiple discontinuous surfaces without using multiple mold pieces. It may be difficult to produce these negative draft angles without using multiple mold pieces, using injection molding techniques, with a curvature that is symmetric about the optical axis, which may be desirable. Machining negative draft angles for the draft surfaces of an optical device with multiple discontinuous surfaces may be expensive.
Producing negative draft angles for the draft surfaces of an optical device with multiple discontinuous surfaces without the expense of using multiple mold pieces may limit the curvature of the optical device that has multiple discontinuous surfaces. Limiting the curvature of the optical device may limit the size and concentration that can be achieved by the optical device, which may have a negative financial and performance impact.